Patient with rapid ascent from lower altitude to higher elevation, usually above 7000 ft. 

Typical Timing of Onset

• AMS (Acute Mountain Sickness) - Usually within 6-24 hours of ascent, will typically resolve spontaneously within 24-36 hours. 

• HACE (High Altitude Cerebral Edema) - Usually within 1-5 days of ascent. Almost always pre-ceeded by symptoms of AMS

• HAPE (High Altitude Pulmonary Edema) - Develops 2-4 days after ascent

• HAFE (High Altitude Flatus Expulsion) - Can Strike at any time without warning.  Has been described even without history of rapid ascent. 

Typical Constellation of Symptoms / Findings

• AMS - Think of a hangover, usually headache (without other neurologic symptoms), nausea/vomiting, fatigue. 

• HACE - Ataxia is earliest sign, usually with headache, severe fatigue / exhaustion, aggression/altered mood

• HAPE -  Dry Cough > Dyspnea with Exertion > Dyspnea at Rest > Pink Frothy Sputum. Crackles heard first at Right middle lobe but may become generalized.  Low grade tachycardia and fever (typically LESS than 38 C) may be present.  Accompanied by symptoms of AMS about 50% of the time.  Hypoxiemia may be severe but should correct quickly with supplemental O2.  Imaging with patchy alveolar infiltrates, may be isolated to Right mid lung or generalized.  Radiographic findings usually are worse than patient's clinical status. 

• HAFE - Spontaneous expulsion of rectal gasses, typically at high altitude due to differential pressures between GI tract and ambient atmosphere.

Hypoxia usually present but otherwise normal vital signs

Other Differential Diagnoses Considered and ruled out

• AMS : Acute viral illness etc

• HACE: Consider ICH, CO poisoning, electrolyte abnormalities, Stroke

• HAPE: Acute heart failure, PE, PNA ruled out

• HAFE: Legume ingestion, FOS (fecal overload syndrome) etc. 

Fever, severe hypertension/hypotension, significant tachycardia

Altered mental status requiring sitter/sedation

Significant lab abnormalities

Hypoxia requiring > 8L/m to maintain sats > 90%

Improved / Resolved Symptoms of AMS or HACE

O2 sats maintained above 90% with 2L or less of supplemental O2 (Or within 2lpm of patients baseline O2 if they use O2 chronically)

Home O2 eval and supplemental tank at time of discharge can be considered if patient still needs O2 but < 2LPM 

Recommend avoid flying until at baseline O2

Recommendations to not reascend 

Unstable vital signs or worsening clinical condition

 Significant lab or imaging abnormalities

 Patient unable to take PO medications or able to safely care for self in home environment.

Alternative diagnosis identified.